The HIV protease inhibitor nelfinavir down-regulates RET signaling and induces apoptosis in medullary thyroid cancer cells

The Potential Role of Virus Infection in the Progression of Thyroid Cancer

Multiple factors have engaged in the progression of thyroid cancer (TC). Recent studies have shown that viral infection can be a critical factor in the pathogenesis of TC. Viruses, such as Epstein-Barr virus (EBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), may play an essential role in the occurrence, development, and even prognosis in TC. This review mainly explored the potential role of viral infection in the progress of TC. The possible mechanisms could be recognizing the host cell, binding to the receptors, affecting oncogenes levels, releasing viral products to shape a beneficial environment, interacting with immune cells to induce immune evasion, and altering the pituitary-thyroid axis. Thus, comprehensive knowledge may provide insights into finding molecular targets for diagnosing and treating virus-related TC.

Therapeutic Potential of Targeting the Cytochrome P450 Enzymes Using Lopinavir/Ritonavir in Colorectal Cancer: A Study in Monolayers, Spheroids and In Vivo Models

Cytochrome P450 (CYP450) enzyme has been shown to be expressed in colorectal cancer (CRC) and its dysregulation is linked to tumor progression and a poor prognosis. Here we investigated the therapeutic potential of targeting CYP450 using lopinavir/ritonavir in CRC. The integrative systems biology method and RNAseq were utilized to investigate the differential levels of genes associated with patients with colorectal cancer. The antiproliferative activity of lopinavir/ritonavir was evaluated in both monolayer and 3-dimensional (3D) models, followed by wound-healing assays. The effectiveness of targeting CYP450 was examined in a mouse model, followed by histopathological analysis, biochemical tests (MDA, SOD, thiol, and CAT), and RT-PCR. The data of dysregulation expressed genes (DEG) revealed 1268 upregulated and 1074 down-regulated genes in CRC. Among the top-score genes and dysregulated pathways, CYPs were detected and associated with poor prognosis of patients with CRC. Inhibition of CYP450 reduced cell proliferation via modulating survivin, Chop, CYP13a, and induction of cell death, as detected by AnnexinV/PI staining. This agent suppressed the migratory behaviors of cells by induction of E-cadherin. Moreover, lopinavir/ritonavir suppressed tumor growth and fibrosis, which correlated with a reduction in SOD/thiol levels and increased MDA levels. Our findings illustrated the therapeutic potential of targeting the CYP450 using lopinavir/ritonavir in colorectal cancer, supporting future investigations on this novel therapeutic approach for the treatment of CRC.

HIV-Infected Patients as a Model of Aging

We appraised the relationship between the biological and the chronological age and estimated the rate of biological aging in HIV-infected patients. Two independent biomarkers, the relative telomere length and iron metabolism parameters, were analyzed in younger (<35) and older (>50) HIV-infected and uninfected patients (control group). In our control group, telomeres of younger patients were significantly longer than telomeres of older ones. However, in HIV-infected participants, the difference in the length of telomeres was lost. By combining the length of telomeres with serum iron, ferritin, and transferrin iron-binding capacity, a new formula for determination of the aging process was developed. The life expectancy of the healthy population was related to their biological age, and HIV-infected patients were biologically older. The effect of antiretroviral HIV drug therapies varied with respect to the biological aging process. IMPORTANCE This article is focused on the dynamics of human aging. Moreover, its interdisciplinary approach is applicable to various systems that are aging.

Effect of the m6ARNA gene on the prognosis of thyroid cancer, immune infiltration, and promising immunotherapy

BACKGROUND

Accumulating evidence suggests that N6-methyladenosine (m6A) RNA methylation plays an important role in tumor proliferation and growth. However, its effect on the clinical prognosis, immune infiltration, and immunotherapy response of thyroid cancer patients has not been investigated in detail.

METHODS

Clinical data and RNA expression profiles of thyroid cancer were extracted from the Cancer Genome Atlas-thyroid carcinoma (TCGA-THCA) and preprocessed for consensus clustering. The risk model was constructed based on differentially expressed genes (DEGs) using Least Absolute Shrinkage and Selection Operator (LASSO) and Cox regression analyses. The associations between risk score and clinical traits, immune infiltration, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Set Enrichment Analysis (GSEA), immune infiltration, and immunotherapy were assessed. Immunohistochemistry was used to substantiate the clinical traits of our samples.

RESULTS

Gene expression analysis showed that 17 genes, except YHTDF2, had significant differences (vs healthy control, P<0.001). Consensus clustering yielded 2 clusters according to their clinical features and estimated a poorer prognosis for Cluster 1 (P=0.03). The heatmap between the 2 clusters showed differences in T (P<0.01), N (P<0.001) and stage (P<0.01). Based on univariate Cox and LASSO regression, a risk model consisting of three high-risk genes (KIAA1429, RBM15, FTO) was established, and the expression difference between normal and tumor tissues of three genes was confirmed by immunohistochemical results of our clinical tissues. KEGG and GSEA analyses showed that the risk DEGs were related mainly to proteolysis, immune response, and cancer pathways. The levels of immune infiltration in the high- and low-risk groups were different mainly in iDCs (P<0.05), NK cells (P<0.05), and type-INF-II (P<0.001). Immunotherapy analysis yielded 30 drugs associated with the expression of each gene and 20 drugs associated with the risk score.

CONCLUSIONS

Our risk model can act as an independent marker for thyroid cancer and provides promising immunotherapy targets for its treatment.

Molecular Mechanisms of HIV Protease Inhibitors Against HPV-Associated Cervical Cancer: Restoration of TP53 Tumour Suppressor Activities

Cervical cancer is a Human Papilloma virus-related disease, which is on the rise in a number of countries, globally. Two essential oncogenes, E6 and E7, drive cell transformation and cancer development. These two oncoproteins target two of the most important tumour suppressors, p53 and pRB, for degradation through the ubiquitin ligase pathway, thus, blocking apoptosis activation and deregulation of cell cycle. This pathway can be exploited for anticancer therapeutic interventions, and Human Immunodeficiency Virus Protease Inhibitors (HIV-PIs) have attracted a lot of attention for this anticancer drug development. HIV-PIs have proven effective in treating HPV-positive cervical cancers and shown to restore impaired or deregulated p53 in HPV-associated cervical cancers by inhibiting the 26S proteasome. This review will evaluate the role players, such as HPV oncoproteins involved cervical cancer development and how they are targeted in HIV protease inhibitors-induced p53 restoration in cervical cancer. This review also covers the therapeutic potential of HIV protease inhibitors and molecular mechanisms behind the HIV protease inhibitors-induced p53-dependent anticancer activities against cervical cancer.

Nelfinavir Induces Cytotoxicity towards High-Grade Serous Ovarian Cancer Cells, Involving Induction of the Unfolded Protein Response, Modulation of Protein Synthesis, DNA Damage, Lysosomal Impairment, and Potentiation of Toxicity Caused by Proteasome Inhibition

Simple Summary

High-grade serous ovarian cancer (HGSOC) accounts for 70% of all ovarian-cancer-related deaths. Mainstay treatment with platinum-based drugs following surgery results in favorable outcomes in the majority of patients; however, in >80% of cases, the disease relapses with eventual drug resistance. As such, urgent development of improved alternative therapies is necessary for HGSOC patients with lower life expectancy. Rapid repurposing of market available drugs for cancer therapy is a cost-effective alternative to bypass the decade-long traditional drug development pipeline. Among potential drug-repurposing candidates, nelfinavir (NFV)—an anti-infective agent to treat acquired immunodeficiency syndrome (AIDS)—has shown anti-cancer effects against diverse cancers; however, its remedial benefits against HGSOC are unknown. In this study, we explored how NFV targets HGSOC cells obtained from patients at platinum-sensitive and -resistant stages. We observed beneficial efficacy elicited by NFV against HGSOC in both disease conditions through multiple mechanistic avenues, suggesting positive drug-repurposing prospects.

Abstract

High-grade serous ovarian cancer (HGSOC) is a significant cause of mortality among women worldwide. Traditional treatment consists of platinum-based therapy; however, rapid development of platinum resistance contributes to lower life expectancy, warranting newer therapies to supplement the current platinum-based protocol. Repurposing market-available drugs as cancer therapeutics is a cost- and time-effective way to avail new therapies to drug-resistant patients. The anti-HIV agent nelfinavir (NFV) has shown promising toxicity against various cancers; however, its role against HGSOC is unknown. Here, we studied the effect of NFV against HGSOC cells obtained from patients along disease progression and carrying different sensitivities to platinum. NFV triggered, independently of platinum sensitivity, a dose-dependent reduction in the HGSOC cell number and viability, and a parallel increase in hypo-diploid DNA content. Moreover, a dose-dependent reduction in clonogenic survival of cells escaping the acute toxicity was indicative of long-term residual damage. In addition, dose- and time-dependent phosphorylation of H2AX indicated NFV-mediated DNA damage, which was associated with decreased survival and proliferation signals driven by the AKT and ERK pathways. NFV also mediated a dose-dependent increase in endoplasmic reticulum stress-related molecules associated with long-term inhibition of protein synthesis and concurrent cell death; such events were accompanied by a proapoptotic environment, signaled by increased phospho-eIF2α, ATF4, and CHOP, increased Bax/Bcl-2 ratio, and cleaved executer caspase-7. Finally, we show that NFV potentiates the short-term cell cycle arrest and long-term toxicity caused by the proteasome inhibitor bortezomib. Overall, our in vitro study demonstrates that NFV can therapeutically target HGSOC cells of differential platinum sensitivities via several mechanisms, suggesting its prospective repurposing benefit considering its good safety profile.

Two Novel Precursors of the HIV-1 Protease Inhibitor Darunavir Target the UPR/Proteasome System in Human Hepatocellular Carcinoma Cell Line HepG2

Background: Several pre-clinical and clinical reports suggest that HIV-1 protease inhibitors, in addition to the antiretroviral properties, possess pleiotropic pharmacological effects including anticancer action. Therefore, we investigated the pro-apoptotic activity in tumor cells of two molecules, RDD-19 and RDD-142, which are hydroxyethylamine derivatives’ precursors of darunavir and several HIV-1 protease inhibitors. Methods: Three hepatoma cell lines and one non-pathological cell line were treated with RDD-19 and RDD-142, and cell viability was assessed. The expression levels of several markers for ER stress, autophagy, cellular ubiquitination, and Akt activation were quantified in HepG2 cells treated with RDD-19 and RDD-142 to evaluate apoptotic and non-apoptotic cell death. Results: RDD-19 and RDD-142 showed a greater dose-dependent cytotoxicity towards the hepatic tumor cell line HepG2 compared to the non-pathological hepatic cell line IHH. Both molecules caused two types of cell death, a caspase-dependent apoptosis, which was ascertained by a series of biochemical and morphological assays, and a caspase-independent death that was characterized by the induction of ER stress and autophagy. The strong increase of ubiquitinated proteins inside the cells suggested that the target of these molecules could be the proteasome and in silico molecular docking analysis that was used to support the plausibility of this hypothesis. Furthermore, cells treated with the two compounds displayed decreased levels of p-AKT, which interferes with cell survival and proliferation. Conclusions: These findings demonstrate that two compounds, RDD-19 and RDD-142, have pleiotropic effects and that they may represent promising anticancer candidates.

Antiretroviral Drugs Impact Autophagy with Toxic Outcomes

Antiretroviral drugs have dramatically improved the morbidity and mortality of people living with HIV (PLWH). While current antiretroviral therapy (ART) regimens are generally well-tolerated, risks for side effects and toxicity remain as PLWH must take life-long medications. Antiretroviral drugs impact autophagy, an intracellular proteolytic process that eliminates debris and foreign material, provides nutrients for metabolism, and performs quality control to maintain cell homeostasis. Toxicity and adverse events associated with antiretrovirals may be due, in part, to their impacts on autophagy. A more complete understanding of the effects on autophagy is essential for developing antiretroviral drugs with decreased off target effects, meaning those unrelated to viral suppression, to minimize toxicity for PLWH. This review summarizes the findings and highlights the gaps in our knowledge of the impacts of antiretroviral drugs on autophagy.

The Anti-Cancer Properties of the HIV Protease Inhibitor Nelfinavir

Simple Summary

To this day, cancer remains a medical challenge despite the development of cutting-edge diagnostic methods and therapeutics. Thus, there is a continual demand for improved therapeutic options for managing cancer patients. However, novel drug development requires decade-long time commitment and financial investments. Repurposing approved and market-available drugs for cancer therapy is a way to reduce cost and the timeframe for developing new therapies. Nelfinavir is an anti-infective agent that has extensively been used to treat acquired immunodeficiency syndrome (AIDS) in adult and pediatric patients. In addition to its anti-infective properties, nelfinavir has demonstrated potent off-target anti-cancer effects, suggesting that it could be a suitable candidate for drug repurposing for cancer. In this review, we systematically compiled the therapeutic benefits of nelfinavir against cancer as a single drug or in combination with chemoradiotherapy, and outlined the possible underlying mechanistic pathways contributing to the anti-cancer effects.

Abstract

Traditional cancer treatments may lose efficacy following the emergence of novel mutations or the development of chemoradiotherapy resistance. Late diagnosis, high-cost of treatment, and the requirement of highly efficient infrastructure to dispense cancer therapies hinder the availability of adequate treatment in low-income and resource-limited settings. Repositioning approved drugs as cancer therapeutics may reduce the cost and timeline for novel drug development and expedite the availability of newer, efficacious options for patients in need. Nelfinavir is a human immunodeficiency virus (HIV) protease inhibitor that has been approved and is extensively used as an anti-infective agent to treat acquired immunodeficiency syndrome (AIDS). Yet nelfinavir has also shown anti-cancer effects in in vitro and in vivo studies. The anti-cancer mechanism of nelfinavir includes modulation of different cellular conditions, such as unfolded protein response, cell cycle, apoptosis, autophagy, the proteasome pathway, oxidative stress, the tumor microenvironment, and multidrug efflux pumps. Multiple clinical trials indicated tolerable and reversible toxicities during nelfinavir treatment in cancer patients, either as a monotherapy or in combination with chemo- or radiotherapy. Since orally available nelfinavir has been a safe drug of choice for both adult and pediatric HIV-infected patients for over two decades, exploiting its anti-cancer off-target effects will enable fast-tracking this newer option into the existing repertoire of cancer chemotherapeutics.

Efavirenz induces DNA damage response pathway in lung cancer

The cell-cycle related genes are potential gene targets in understanding the effects of efavirenz (EFV) in lung cancer. The present study aimed at investigating the expression changes of cell-cycle related genes in response to EFV drug treatment in human non-small cell lung carcinoma (A549) and normal lung fibroblast (MRC-5) cells. The loss in nuclear integrity in response to EFV was detected by 4', 6-diamidino-2-phenylindole (DAPI) staining. Gene expression profiling was performed using human cell cycle PathwayFinder RT² Profiler™ PCR Array. The expression changes of 84 genes key to the cell cycle pathway in humans following EFV treatment was examined. The R² PCR Array analysis revealed a change in expression of selected gene targets (including MAD2L2, CASP3, AURKB). This change in gene expression was at least a two-fold between test (EFV treated) and the control. RT-qPCR confirmed the PCR array data. In addition to this, the ATM signaling pathway was shown to be upregulated following EFV treatment in MRC-5 cells. In particular, ATM's upstream activation resulted in p53 upregulation in normal lung fibroblasts. Interestingly, the p53 signaling pathway was activated irrespective of the repressed ATM pathway in A549 cells as revealed by the Ingenuity Pathway Analysis (IPA). These EFV effects are similar to those of ionizing radiation and this suggests that EFV has anti-tumour properties.

The dual protease inhibitor lopinavir/ritonavir (LPV/r) exerts genotoxic stress on lung cells

The Sub-Saharan countries, particularly South Africa has the largest number of people living with HIV, accompanied by the largest antiretroviral treatment (ART) programme in the world. The Highly Active Antiretroviral Treatment (HAART) is the most effective regimen against HIV/AIDS and has improved the lifespan and quality of life of HIV positive patients. HAART has also led to a decrease in the incidence of AIDS defining cancers (ADCs) while there is an increased incidence of the non-AIDS Defining Cancers (NADCs), such as lung cancer in the HAART era. The association between lung tumourigenesis and the use of HAART components such as the dual protease inhibitor (PI) lopinavir/ritonavir (LPV/r) is poorly understood. Using cell and molecular biological approaches, this study aimed at elucidating the effects of LPV/r on the regulation of the cell cycle related genes in normal (MRC-5) and adenocarcinoma (A549) lung cells. Initially, the nuclear integrity of these cells in response to LPV/r was determined using DAPI staining. The effect of LPV/r on cell cycle genes was evaluated through the use of a RT2 PCR gene array of 84 genes related to the cell cycle signaling pathway. The PCR array data was validated by Real-Time Quantification PCR (RT-qPCR). Ingenuity Pathway Analysis (IPA) bio-informatics tool was employed to disclose the molecular mechanism/s observed at cellular and gene expression levels. Loss of nuclear integrity and the upregulation of the p53 DNA damage response (DDR) pathway was revealed by DAPI staining, differential gene expression and IPA core analysis. Furthermore, MAD2L2 and AURKB which also play a role in the DDR pathway were shown to be differentially expressed. The activation of the CASP3 gene in response to LPV/r in A549 cells was also observed. The findings of this study suggest genotoxic properties of LPV/r in healthy normal lung fibroblasts cells and anti-tumour properties in the A549 cells.

13-Methylberberine improves endothelial dysfunction by inhibiting NLRP3 inflammasome activation via autophagy induction in human umbilical vein endothelial cells

Background

Atherosclerosis, the underlying cause of the majority of cardiovascular diseases, is a lipid-driven, inflammatory disease of the large arteries. Atherosclerotic cardiovascular disease (ASCVD) threatens human lives due to high morbidity and mortality. Many studies have demonstrated that atherosclerosis is accelerated via activation of the NLRP3 inflammasome. The NLRP3 inflammasome plays a critical role in the development of vascular inflammation and atherosclerosis. In atherosclerotic plaques, excessive generation of reactive oxygen species (ROS) activates the NLRP3 inflammasome. 13-Methylberberine (13-MB) is a newly synthesized compound used in traditional Chinese medicine that has outstanding antibacterial, antitumor, and antiobesity activities, especially anti-inflammatory activity. However, the role of 13-MB in atherosclerosis needs to be explored.

Methods

CCK-8 assays and flow cytometry were conducted to determine the cell viability and apoptotic profiles of human umbilical vein endothelial cells (HUVECs) treated with 13-MB. Carboxy-DCFH-DA and JC-10 assays were used to measure ROS and determine mitochondrial membrane potential. Western blot analysis was performed to investigate proteins that are associated with the NLRP3 inflammasome and autophagy. ELISA was used to detect and quantify inflammatory cytokines related to the NLRP3 inflammasome. Transfection and confocal microscopy were conducted to observe autophagy.

Results

Pretreatment with 13-MB markedly reduced cytotoxicity and apoptosis, as well as intracellular ROS production, in H₂O₂-induced HUVECs. Moreover, 13-MB showed a protective effect in maintaining mitochondrial membrane potential. 13-MB also suppressed NLRP3 inflammasome activation and promoted autophagy induction in HUVECs.

Conclusion

13-MB exerts cytoprotective effects in an H₂O₂-induced cell injury model by inhibiting NLRP3 inflammasome activation via autophagy induction in HUVECs. These anti-inflammatory and autophagy induction activities may provide valuable evidence for further investigating the potential role of 13-MB in atherosclerosis.

Mitotane induces mitochondrial membrane depolarization and apoptosis in thyroid cancer cells

Mitotane is used for the treatment of adrenocortical cancer and elicits its anticancer effects via inhibition of mitochondrial respiration. Targeting mitochondria‑dependent metabolism has emerged as a promising strategy for thyroid cancer (TC) treatment. We hypothesized that mitotane targets mitochondria and induces apoptosis in TC cells. Cell lines representative of the major histological variants of TC were chosen: Follicular (FTC‑133), poorly differentiated (BCPAP), anaplastic (SW1736 and C643) and medullary (TT) TC cells, and were treated with mitotane (0‑100 µM). Mitochondrial membrane potential, cell viability and apoptosis were examined by JC‑1 staining and by western blot analysis using an antibody against caspase‑3. The expression of mitochondrial molecules and DNA damage markers and the activation of endoplasmic reticulum (ER) stress were determined by western blotting. The expression of mitochondrial ATP synthase subunit β (ATP5B) was examined by immunostaining in 100 human TC tissue samples. Treatment with mitotane (50 µM for 24 h) decreased the viability of FTC‑133, BCPAP, SW1736, C643 and TT cells by 12, 59, 54, 31 and 66%, respectively. Morphological evidence of ER stress and overexpression of ER markers was observed in TC cells following exposure to mitotane. The treatment led to increased expression of histone γH2AX, indicating DNA damage, and to caspase‑3 cleavage. Consistent with the results of the cell viability assays, the overexpression of pro‑apoptotic genes following treatment with mitotane was more prominent in TC cells harboring mutations in the serine/threonine‑protein kinase B‑raf gene and proto‑oncogene tyrosine‑protein kinase receptor Ret. Treatment with mitotane was associated with loss of mitochondrial membrane potential and decreased expression of ATP5B, particularly in the medullary TC (MTC)‑derived TT cells. Immunohistochemical analysis of mitochondrial ATP5B in human TC specimens demonstrated its overexpression in cancer compared with normal thyroid tissue. The level of ATP5B expression was higher in MTC compared with the follicular, papillary or anaplastic types of TC. Mitotane elicited pleiotropic effects on TC cells, including induction of ER stress, inhibition of mitochondrial membrane potential and induction of apoptosis. The results of the present study suggest that mitotane could be considered as a novel agent for the treatment of aggressive types of TC.

Lopinavir-NO, a nitric oxide-releasing HIV protease inhibitor, suppresses the growth of melanoma cells in vitro and in vivo

We generated a nitric oxide (NO)-releasing derivative of the anti-HIV protease inhibitor lopinavir by linking the NO moiety to the parental drug. We investigated the effects of lopinavir and its derivative lopinavir-NO on melanoma cell lines in vitro and in vivo. Lopinavir-NO exhibited a twofold stronger anticancer action than lopinavir in vitro. These results were successfully translated into syngeneic models of melanoma in vivo, where a significant reduction in tumour volume was observed only in animals treated with lopinavir-NO. Both lopinavir and lopinavir-NO inhibited cell proliferation and induced the trans-differentiation of melanoma cells to Schwann-like cells. In melanoma cancer cell lines, both lopinavir and lopinavir-NO induced morphological changes, minor apoptosis and reactive oxygen species (ROS) production. However, caspase activation and autophagy were detected only in B16 cells, indicating a cell line-specific treatment response. Lopinavir-NO released NO intracellularly, and NO neutralization restored cell viability. Treatment with lopinavir-NO induced only a transient activation of Akt and inhibition of P70S6 kinase. The results of this study identify lopinavir-NO as a promising candidate for further clinical trials in melanoma and possibly other solid tumours.

Transcriptional targeting of oncogene addiction in medullary thyroid cancer

Metastatic medullary thyroid cancer (MTC) is incurable and FDA-approved kinase inhibitors that include oncogenic RET as a target do not result in complete responses. Association studies of human MTCs and murine models suggest that the CDK/RB pathway may be an alternative target. The objective of this study was to determine if CDKs represent therapeutic targets for MTC and to define mechanisms of activity. Using human MTC cells that are either sensitive or resistant to vandetanib, we demonstrate that palbociclib (CDK4/6 inhibitor) is not cytotoxic to MTC cells but that they are highly sensitive to dinaciclib (CDK1/2/5/9 inhibitor) accompanied by reduced CDK9 and RET protein and mRNA levels. CDK9 protein was highly expressed in 83 of 83 human MTCs and array-comparative genomic hybridization had copy number gain in 11 of 30 tumors. RNA sequencing demonstrated that RNA polymerase II-dependent transcription was markedly reduced by dinaciclib. The CDK7 inhibitor THZ1 also demonstrated high potency and reduced RET and CDK9 levels. ChIP-sequencing using H3K27Ac antibody identified a superenhancer in intron 1 of RET. Finally, combined inhibition of dinaciclib with a RET kinase inhibitor was synergistic. In summary, we have identified what we believe is a novel mechanism of RET transcription regulation that potentially can be exploited to improve RET therapeutic targeting.

Reduced Retinoblastoma Protein Expression Is Associated with Decreased Patient Survival in Medullary Thyroid Cancer

BACKGROUND

The retinoblastoma (RB) transcriptional corepressor 1 protein functions to slow cell-cycle progression. Inactivation of RB by reduced expression and/or hyperphosphorylation allow for enhanced progression through the cell cycle. Murine models develop medullary thyroid carcinoma (MTC) after generalized loss of RB. However, RB expression in MTC has only been evaluated in a small number of tumors, with differing results. The objective of this study was to determine whether reduced expression of RB and/or overexpression of hyperphosphorylated RB predict MTC aggressive behavior.

METHODS

Formalin-fixed, paraffin-embedded primary thyroid tumors and lymph node metastases from MTC patients were evaluated for calcitonin, RB, and phosphorylated RB (pRB) expression by immunohistochemistry. Two expert pathologists evaluated the slides in a blinded manner, and the immunohistochemistry results were compared to disease-specific survival as a primary endpoint.

RESULTS

Seventy-four MTC samples from 56 patients were analyzed in this study, including 51 primary tumors and 23 lymph node metastases. The median follow-up time was 6.75 years after surgery (range 0.64-24.30 years), and the median primary tumor size was 30 mm (range 6-96 mm). Sixty-six percent of cases were classified as stage IV. RB nuclear expression was diffusely present in 88% of primary tumors and 78% of lymph node metastases. Nuclear pRB expression was present in 22% of primary tumors and 22% of lymph node metastases. On univariate analysis, reduced RB (<75% tumor cell staining) trended with lower MTC-specific survival for primary tumor and metastatic nodes (primary tumor hazard ratio = 3.54 [confidence interval 0.81-15.47], p = 0.08; and lymph node hazard ratio = 4.35 [confidence interval 0.87-21.83], p = 0.05). For primary tumors, multivariable analysis showed that low nuclear RB expression was independently associated with worse disease-specific (p = 0.01) and overall (p = 0.02) survival. pRB levels were not associated with survival for either primary tumor or lymph node metastases.

CONCLUSIONS

Reduced RB expression is associated with decreased patient survival in univariate and multivariable analyses, independent from patient age at surgery or advanced TNM stage. Future studies involving larger MTC patient populations are warranted to determine if lower RB expression levels may serve as a biomarker for aggressive disease in patients with MTC.

Targeted Therapy for Medullary Thyroid Cancer: A Review

Medullary thyroid cancers (MTCs) constitute between 2 and 5% of all thyroid cancers. The 10-year overall survival (OS) rate of patients with localized disease is around 95% while that of patients with regional stage disease is about 75%. Only 20% of patients with distant metastases at diagnosis survive 10 years which is significantly lower than for differentiated thyroid cancers. Cases with regional metastases at presentation have high recurrence rates. Adjuvant external radiation confers local control but not improved OS. The management of residual, recurrent, or metastatic disease till a few years ago was re-surgery with local measures such as radiation. Chemotherapy was used with marginal benefit. The development of targeted therapy has brought in a major advantage in management of such patients. Two drugs—vandetanib and cabozantinib—have been approved for use in progressive or metastatic MTC. In addition, several drugs acting on other steps of the molecular pathway are being investigated with promising results. Targeted radionuclide therapy also provides an effective treatment option with good quality of life. This review covers the rationale of targeted therapy for MTC, present treatment options, drugs and methods under investigation, as well as an outline of the adverse effects and their management.

Nelfinavir inhibits proliferation and induces DNA damage in thyroid cancer cells

The HIV protease inhibitor Nelfinavir (NFV) inhibits PI3K/AKT and MAPK/ERK signaling pathways, emerging targets in thyroid cancers. We examined the effects of NFV on cancer cells that derived from follicular (FTC), papillary (PTC) and anaplastic (ATC) thyroid cancers. NFV (1-20 µM) was tested in FTC133, BCPAP and SW1736 cell lines. The effects of NFV on cell proliferation were determined in vitro using real-time microscopy and by flow cytometry. DNA damage, apoptotic cell death and expression of molecular markers of epithelial-mesenchymal transition (EMT) were determined by Western blot and real-time PCR. Real-time imaging demonstrated that NFV (10 µM) increased the time required for the cell passage through the phases of cell cycle and induced DNA fragmentation. Growth inhibitory effects of NFV were associated with the accumulation of cells in G0/G1 phase, downregulation of cyclin D1 and cyclin-dependent kinase 4 (CDK4). NFV also induced the expression of γH2AX and p53BP1 indicating DNA damage. Treatment with NFV (20 µM) resulted in caspase-3 cleavage in all examined cells. NFV (20 µM) decreased the levels of total and p-AKT in PTEN-deficient FTC133 cells. NFV had no significant effects on total ERK and p-ERK in BRAF-positive BCPAP and SW1736 cells. NFV had no effects on the expression of EMT markers (Twist, Vimentin, E- and N-Cadherin), but inhibited the migration and decreased the abilities of thyroid cancer cells to survive in non-adherent conditions. We conclude that NFV inhibits proliferation and induces DNA damage in thyroid cancer cell lines. Our in vitro data suggest that NFV has a potential to become a new thyroid cancer therapeutic agent.

HIV-protease inhibitors for the treatment of cancer: Repositioning HIV protease inhibitors while developing more potent NO-hybridized derivatives?

The possible use of HIV protease inhibitors (HIV-PI) as new therapeutic option for the treatment of cancer primarily originated from their success in treating HIV-related Kaposi's sarcoma (KS). While these findings were initially attributed to immune reconstitution and better control of oncogenic viral infections, the number of reports on solid tumors, KS, lymphoma, fibrosarcoma, multiple myeloma and prostate cancer suggest other mechanisms for the anti-neoplastic activity of PIs. However, a major drawback for the possible adoption of HIV-PIs in the therapy of cancer relies on their relatively weak anticancer potency and important side effects. This has propelled several groups to generate derivatives of HIV-PIs for anticancer use, through modifications such as attachment of different moieties, ligands and transporters, including saquinavir-loaded folic acid conjugated nanoparticles and nitric oxide (NO) derivatives of HIV-PIs. In this article, we discuss the current preclinical and clinical evidences for the potential use of HIV-PIs, and of novel derivatives, such as saquinavir-NO in the treatment of cancer.

Regulation of SREBP-2 intracellular trafficking improves impaired autophagic flux and alleviates endoplasmic reticulum stress in NAFLD

Sterol regulatory element-binding protein 2 (SREBP-2), is a well-known transcriptional regulator of cholesterol metabolism. SREBP-2 is activated unconventionally to promote excessive cholesterol accumulation in non-alcoholic fatty liver disease (NAFLD). In addition, recent studies suggested that excessive lipid and cholesterol accumulation can weaken cellular autophagy function and promote endoplasmic reticulum stress (ERS). However, it remains unknown whether regulation of SREBP-2 processing modulates autophagy and ERS. In this study, we demonstrated that inhibition of SREBP-2 intracellular trafficking by site-1 protease (S1P) and site-2 protease (S2P) specific inhibitors, or shRNAs targeting S1P and S2P, upregulated gene and protein expression of autophagy markers, and improved the impaired autophagic flux induced in both cell and mouse models of NAFLD. Furthermore, increased lipid degradation by autophagy could repress PERK-P-EIF2α signaling. Taken together, these findings suggest that regulating the nuclear transport of SREBP-2 reduces lipid deposition and ERS via an autophagy-dependent pathway.

Induction of DNA damage and apoptosis in human leukemia cells by efavirenz

As part of the efforts to drug repurposing, some HIV drugs have recently been identified to exert anticancer effects. Selected nucleoside analogues of nucleosidic reverse-transcriptase inhibitors (NRTIs) have been shown to interfere with RNA transcription of HI viruses as well as with the replication of DNA in cancer cells. Non-nucleosidic reverse transcriptase inhibitors (NNRTIs) are believed to have less effects on human DNA replication and, thus, on cancer cell proliferation. Assessment of the effect of the NNRTI efavirenz in human cancer cells, however, revealed a high sensitivity of leukemia cells to this agent at pharmacologically relevant concentrations of less than 10 µg/ml. Cell death induced by efavirenz was caused by apoptosis, as shown by FACScan analysis (Annexin binding) and western blot analysis (cleavage of caspases and PARP). Western blot analyses also revealed a pronounced activation and phosphorylation of the DNA damage marker proteins p53, chk2 and H2AX, indicating DNA replication and genomic integrity as primary targets of efavirenz in leukemia cells.

Endocrine tumours: progressive metastatic medullary thyroid carcinoma: first- and second-line strategies

The treatment for metastasised medullary thyroid cancer is still a topic of discussion. One of the main challenges remains to find effective adjuvant and palliative options for patients with metastatic disease. The diagnostic and treatment strategies for this tumour are discussed and possible new developments commented. Approaches that target rearranged during transfection (RET) are preferable to those that target RET downstream proteins as, theoretically, blocking RET downstream targets will block only one of the many pathways activated by RET. Combining several agents would seem to be more promising, in particular agents that target RET with those that independently target RET signalling pathways or the more general mechanism of tumour progression.

Induction of suicidal erythrocyte death by nelfinavir

The HIV protease inhibitor, nelfinavir, primarily used for the treatment of HIV infections, has later been shown to be effective in various infectious diseases including malaria. Nelfinavir may trigger mitochondria-independent cell death. Erythrocytes may undergo eryptosis, a mitochondria-independent suicidal cell death characterized by cell shrinkage and phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include oxidative stress and increase of cytosolic Ca²⁺-activity ([Ca²⁺]_i). During malaria, accelerated death of infected erythrocytes may decrease parasitemia and thus favorably influence the clinical course of the disease. In the present study, phosphatidylserine abundance at the cell surface was estimated from annexin V binding, cell volume from forward scatter, reactive oxidant species (ROS) from 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence, and [Ca²⁺]_i from Fluo3-fluorescence. A 48 h treatment of human erythrocytes with nelfinavir significantly increased the percentage of annexin-V-binding cells (≥5µg/mL), significantly decreased forward scatter (≥2.5µg/mL), significantly increased ROS abundance (10 µg/mL), and significantly increased [Ca²⁺]_i (≥5 µg/mL). The up-regulation of annexin-V-binding following nelfinavir treatment was significantly blunted, but not abolished by either addition of the antioxidant N-acetylcysteine (1 mM) or removal of extracellular Ca²⁺. In conclusion, exposure of erythrocytes to nelfinavir induces oxidative stress and Ca²⁺ entry, thus leading to suicidal erythrocyte death characterized by erythrocyte shrinkage and erythrocyte membrane scrambling.

Nelfinavir and other protease inhibitors in cancer: mechanisms involved in anticancer activity

OBJECTIVE

To review the mechanisms of anti-cancer activity of nelfinavir and other protease inhibitors (PIs) based on evidences reported in the published literature.

METHODS

We extensively reviewed the literature concerning nelfinavir (NFV) as an off target anti-cancer drug and other PIs. A classification of PIs based on anti-cancer mode of action was proposed. Controversies regarding nelfinavir mode of action were also addressed.

CONCLUSIONS

The two main mechanisms involved in anti-cancer activity are endoplasmic reticulum stress-unfolded protein response pathway and Akt inhibition. However there are many other effects, partially dependent and independent of those mentioned, that may be useful in cancer treatment, including MMP-9 and MMP-2 inhibition, down-regulation of CDK-2, VEGF, bFGF, NF-kB, STAT-3, HIF-1 alfa, IGF, EGFR, survivin, BCRP, androgen receptor, proteasome, fatty acid synthase (FAS), decrease in cellular ATP concentration and upregulation of TRAIL receptor DR5, Bax, increased radiosensitivity, and autophagy. The end result of all these effects is slower growth, decreased angiogenesis, decreased invasion and increased apoptosis, which means reduced proliferation and increased cancer cells death. PIs may be classified according to their anticancer activity at clinically achievable doses, in AKT inhibitors, ER stressors and Akt inhibitors/ER stressors. Beyond the phase I trials that have been recently completed, adequately powered and well-designed clinical trials are needed in the various cancer type settings, and specific trials where NFV is tested in association with other known anti-cancer pharmaceuticals should be sought, in order to find an appropriate place for NFV in cancer treatment. The analysis of controversies on the molecular mechanisms of NFV hints to the possibility that NFV works in a different way in tumor cells and in hepatocytes and adipocytes.

Endoplasmic reticulum stress and cell death in mTORC1-overactive cells is induced by nelfinavir and enhanced by chloroquine

Inappropriate activation of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) is common in cancer and has many cellular consequences including elevated endoplasmic reticulum (ER) stress. Cells employ autophagy as a critical compensatory survival mechanism during ER stress. This study utilised drug-induced ER stress through nelfinavir in order to examine ER stress tolerance in cell lines with hyper-active mTORC1 signalling. Our initial findings in wild type cells showed nelfinavir inhibited mTORC1 signalling and upregulated autophagy, as determined by decreased rpS6 and S6K1 phosphorylation, and SQTSM1 protein expression, respectively. Contrastingly, cells with hyper-active mTORC1 displayed basally elevated levels of ER stress which was greatly exaggerated following nelfinavir treatment, seen through increased CHOP mRNA and XBP1 splicing. To further enhance the effects of nelfinavir, we introduced chloroquine as an autophagy inhibitor. Combination of nelfinavir and chloroquine significantly increased ER stress and caused selective cell death in multiple cell line models with hyper-active mTORC1, whilst control cells with normalised mTORC1 signalling tolerated treatment. By comparing chloroquine to other autophagy inhibitors, we uncovered that selective toxicity invoked by chloroquine was independent of autophagy inhibition yet entrapment of chloroquine to acidified lysosomal/endosomal compartments was necessary for cytotoxicity. Our research demonstrates that combination of nelfinavir and chloroquine has therapeutic potential for treatment of mTORC1-driven tumours.